Method of translating heat energy into motive power



0v. 1@, 1942., H L v 2,391,404

METHOD OF TRANSLATING HEAT ENERGY INTO MOTIVE POWER 7 Filed March 20, 1939 3 Sheets-Sheet l IN VEN TOR.

BRADFORD 5. HOLMES ATTORNEY.

Nov. 10, 1942.

' 3. B. HOLMES I 2,301,404

METHOD OF TRANSLATING HEAT ENERGY INTO MOTIVE POWER Filed March 20, 1939 3 Sheets-Sheet 2 mix/L 1 2v rweams PRESSURE LBS/$9.1M Am.

FIG 6 14-? B2 W B INVENTOR.

a m BRADFORD B. HOLMES ATTORNEY.

Nov. 1%,1'942. a LME Q 2,391,404

METHOD OF TRANSLATING HEAT ENERGY INTO MOTIVE POWER JNVENTOR. BRADFORD 5. Homes BY g ATTORNEK.

Patented Nov. 10, 1942 I METHOD OF TRAN SLATING HEAT ENERGY INTO MOTIVE POWER Bradford B. Holmes, New York, N. r. Application March 20, 1939, Serial No. 263,061

Claims.

The present invention relates to a novel method of converting heat into motive power, and more particularly to a novel method of powering a propeller-driven aircraft by vaporizing, superheating, expanding and liquefying a novel working fluid, and utilizing the expansion of the fluid' vapor to operate a turbine for driving the propeller.

Various fluids such as alcohols, analine, benzol, carbon tetrachloride, ether, sulphur dioxide, toluol, water and xylol have been suggested heretofore for use as a working fluid for converting heat into motive power by a thermodynamic cycle of vaporizing, superheating, expanding and liquefying said fluid, but all such prior art fluids have many serious disadvantages and drawbacks which render them impractical ordangerous and, therefore, unsuitable for commercial use, especially for operating a power plant of an aircraft such as a passenger airliner, for example, where space is necessarily limited; reduction of weight extremely important, and utmost safety to passengers and crew absolutely essential.

The principal disadvantages of such prior art working fluids are that either their critical temperatures and pressures are entirely too high for practical purposes, requiring tremendous volumes of liquid, thereby necessitating extremely large and heavy boilers and pipes, or they are highly toxic, corrosive, inflammable and combustible, hereby rendering their use very dangerous to human life and property and causing rapid deterioration of the equipment, or they are too volatile and do not provide enough kinetic energy to produce sumcient power, especially the great amount of power that is require inan aircraft engine.

Moreover, none of the prior art fluids that have been suggested for use as working fluids for converting heat into motive power has thermodynamic properties suitable for driving a turbine and plotting of heat-pressure diagrams of a series of fluids containing various chemical combinatlons of carbon, chlorine and fluorine, that these fluids have excellent physical and thermodynamic properties which render them extremely suitable and highly desirable for use as a working fluid for converting heat into motive power by a thermo ynamic cycle of vaporizing, superheating, ex-

V *pa'nding and liquefying the fluid.

These fluids are known as "Freons and the ones found suitable for the above-mentioned purpose are, for example, Freons- F-ll which is is trichloro-monofluoro-methane .(CClaF) F-12 which is dichloro-difluoro-methane (CCI2F2),

'F21-' which is dichloro-monofluoro-methane (CHClzF) and F--113 which is trichloro-trifiuoroethane (CzClaFa) The following table gives data on these four fluid substances:

. T"-l2 F--2l F-11 F -ll3 Name D ichloru- Dicllloro- Trlchloro- Trlchlorodifluoromonofluoromonofiuorotrlfluoromethane methane methane ethane Formula COM CHChF CChF C2G13F3 Melting point... -252 F. -2ll F. -168 F. .3l F. Abs. critical pressure 582 750 635 499 Critical tcmpor- 'ature 233 F 353 F. 388 F. 417 F Absolute pressure. at

5 26. 5 5. 243 2. 931 9802 51.7 12.32 7.032 2. 655 W7. 9 31. 23 18. 28 7. 856 100 131. 6 40. 04 23. 10,48 Density at 86 2. 569 577C 5666 3360 All of the above-listed fluids are non-tome,

non-combustible and non-corrosive to metal, and each has a low melting point, low critical temperature and low critical pressure, thereby making them suitable 'for the purpose of the present invention. The choice of fluid for powering ,an airplane largely depends upon the prevailing condensing temperature, whether the craft is traveling at sub-zero conditions or higher temperatures, and upon thethermal efliciency obtainable from the fluid under the prevailing conditions. That is, an airplane operated in the winter or at high altitudes might use one fluid, whereas in summer or at low altitudes, another of the Freons might be used to better advantage.

Accordingly, one of the objects of the present. invention is to provide a novel method of converting heat into motive power by vaporizing, superheating, expanding and liquefying a novel working fluid comprising carbon, chlorine and fluorine in stable chemical combination and which is non-volatile, non -corrosive, non-combustible,

andnecessary on aircraft.

2 flciency and utmost-safety which is so desirable Another object of the invention is to provide a novel method of powering a propeller-driven aircraft by. converting heat into motive power by a thermodynamic cycle of vaporizing, superheating,

The condensed pipe 40, flows countercurrent to the heating draft,

expanding and liquefying a working fluid, which square inch while in the liquid state, heating said liquid to a temperature between 200 F. and 420" F. to vaporize it without boiling, superheating the vapor to a temperature high enough to ensure dry vapor throughout the desired expansion range, expanding said vapor to a desired condensing pressure, utilizing the expansion of said vapor to drive the aircraft propeller, condensing said vapor to a liquid, and continuously repeating the cycle.

The foregoing tages of theinvention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein one form of apparatus for carrying out the invention and for applying it thereto is illustrated by way of example. It is to be expressly understood, howto a pressure between 400 and 1000 pounds per first. throughthe outer helix of the coil where the progressively cooled products of combustion are coolest,- then through the inner helix to its exit end, where the heat is most intense. Thus the liquid is progressively heated to maximum, while the countercurrent products of combustion are progressively cooled until the highly heated fluid flows out through the-pipe H2. The flame is controlled by a metal thermostatic element I I4, which governs the valve I04 to keep constant the temperature of the vapor leaving the heater. Thence the vapor flows through pipe H2 and throttle valve I to turbine I9, where it is expanded. Thence the expanded vapor enters the and other objects and-advan- V ever, that the drawings are only for the purpose of showing the manner of carrying out and applying the novel method of the invention, and

are not to be construed as defining the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings. wherein like reference characters refer to like parts:

Fig. 1 is a plan view-showing diagrammatically an aeroplane with single propeller equipment powered according to the method of the present invention;

Fig. 2 is a similar view with turbines for two propellers and for auxiliary power;

' Fig.3 is a diagrammatic horizontal cross-section of a turbo-propeller;

F'". 4 s a we a "ac on rm i e 4-4. Fig. 3; Fi 5 shows the details of an automatic shutoff valve:

Fig. 6 is a pressure-heat Mollier d agram of F--II on which is superimposed the cycle of an illustrative example; and

Fig. '7 is a schematic diagram of a turbine and heater showing the heater in vertical cross-sec-' tion.

In Figs. 1, 2 and 7, the essential elements are indicated by similar reference numerals.

space 23, where it encounters the regenerator'coil 24, wherein the condensate absorbs heat from said vapo 1 From regenerator coil 24, cooled vapor following the path of the arrows, enters the'condenser chamber 20a, which is the whole space within the boundary walls 28, of the unit, except the space occupiedfby the turbine, and except space '21 which'contains the reduction gears 20, 2|.

The vapor condenses on the surface 28 and collects at the bottom, whence it flows through inlet 00, pipe 35, and pump 4I which forces the liquid through pipe 36. and through the above described regenerator coilf24, wherein the liquid is heated by the exhaust from the turbine. Pressure applied by pump M is controlled by a pressure reliefvalve 42 which can be set for any desiredpressure that may be necessary to raise the heater output fluid to the desired pressure. The heated liquid raised to the high pressure required in the heater, is forced from pipe 24 through pipe 40, to the intake IOI, of heater coil I00.

While, as above explained, there isvery great advantage in having this pressure above critical so that the liquid may be all changed to vapor condition without boiling, inspection of the M01- lier diagram, Fig. 6, shows that the latent heat rate of revolution required for the propeller. As shown, pump H is geared directly to the propeller In Fig. 1, the method of the invention is applied, by way of 'example, to the powering of an aeroplane I0 shown as equipped with a heater II containing a continuous coil I00, of seamless tubing. The exit section of this coil iswound around a cylindrical core I08 of high heat conductivity such as copper; and the entrance section is coiled in a larger-diameter helix extending in the opposite direction, adjacent the outer casing. Between the two helices of the mills a cylindrical partition Ila closed in at the end by baiile plate IIb. An oil nozzle I03 controlled by a valve in I04 directs a flame axially of the copper cylinder I08, and the hot'products of combustion flow reversely, outside the copper cylinder, along the exit helix of the coil, then again reversely,

outside. of partition Ila, along the outer entrance helix, as indicated by the arrows.

of vaporization decreases with rise of pressure and becomes zero at the critical pressure. g

It is therefore obvious that the heater may be used with pressures below the critical provided they are not so much below that excessive boil- 7 ing occurs.

The turbine drives the pinion 20 which meshes I with the large gear 2I on the propeller shaft, thereby reducing the turbine revolutions to the shaft.

All of the above'elements, as diagrammatically indicated in Fig. 1, are embodied in diagram- -matic Fig. 7 and also less diagrammatic Figs. 2,

-3, '4 and 5; and for this reason such elements as are indicated in the latter figures are. designated by the same numerals as'in Fig. 1.

. Referring to said Fig. '7, and also to Figs. 2, 3, 4 and 5, it will be seen that as before, the heater II comprises acontinuous coil of-seamless'tubing. preferably Monel metal, or a number of such coils, preferablyin parallel, having an inlet IOI andan outlet I02. Heat is applied to the. heater from fuel oil burned in the oil burner I03. This may be of any conventional form-and comprises a throttling valve I04, oil pump I05, blower I00, and motor I01. That part of the coil I00 which is nearest the flame is wound around a core I00 of high heat conductivity metal, such as copper, to prevent any part of the tube from becoming so highly heated liquid is forced through suppl 1 as to endanger. the chemical stability the work- A liquid receiver 31, contains a supply of working liquid and is preferably placed in that part of the heater nearest the stack so that it can absorb any available heat remaining in the furnace gases. A liquid pump 4|, which may be any conventional rotary or piston pump, pumps liquid from the receiver 31,into the heater I l, via pipes I09 and I II). A by-pass relief valve 42, which can be set for any desired pressure, such as 800 lbs., prevents that pressure from being exceeded in the heater.

The pump 4| may be electrically driven by a motor I energized from a battery as shown in Fig. '7 of the drawings.

The liquid entering at it! passes through the tube Hill, gaining temperature and heat content substantially uniformly, and passes from a liquid to a vapor without boiling as soon as its critical temperature is reached, because it is being heated at a pressure level above its critical pressure, and acquires superheat until the desired temperature is reached and escapes at 02 via pipe H2.

The hot gases from the flame travel in a countercurrenlt direction to the working fluid, losing heat and temperature substantially uniformly; and they leave at-H3 not greatly hotter than the incoming liquid,

In order to maintain a constant temperature in the outgoing working fluid, a thermostat comprising a bimetallic strip H4 embedded in the core I 08 governs the oil valve I04 to maintain a substantially constant temperature in I08.

Pipe I 12 connects at H5 with pipes l2, l3 and i l carrying the vapor to the turbo-propeller units l5 and It, and auxiliary turbine 99, and valves i1 and [8, are manipulated by the operator to control the opening and closing of the turbine nozzles for regulating engine power.

The turbine I9 is shown diagrammatically in Fig. 3. It drives a gear, 20, which'operates the reduction gear, 21, to which the propeller, 22, is attached.

After the vapor has been expanded in the turbine it enters space 23, where is encounters a regenerator coil which absorbs superheat from the vapor, as. described below. The cooled vapor then following the path of the arrows, enters the condenser chamber 25a at 25. The condenser chamber is the whole space within the boundary walls 28, of the unit, except the space occupied by the turbine and the space 21, which contains the reduction gears 2|. Space 2! is isolated from the rest of the condenser to prevent the condensed liquid from interfering with the lubrication of the gears.

The vapor condenses all over the surface 26. and collects in the bottom. Tw o liquid outlets 30, one at the end of each of the arms 29, are provided. They are closed byvalves 3|, on arms 32. Floats 33 cause the valves to open when enough liquid has collected to raise the floats. The two valved liquid outlets so located, are necessary because there are times when the plane mill is not level or when it is not perpendicular to v through the submerged outlet, whatever the aspect of the plane.

The liquid is sucked through pipes 35, by the sump pump 34, which can be a rotary pump driven by the propeller shaft, and is delivered through pipe 36, to one end of the regenerator coil 24, where it travels in coun-tercurrent relation to the exhaust vapor and picks up the superheat remaining in it. It then flows to the liquid receiver 31, via pipes 38, 39 and 40.

As already stated, pressure pump 4| takes liquid from the receiver and pumps it into the heater H. The pump 4! can conveniently be an electric driven rotary gear pump, deriving its power from the auxiliary turbine, 99. This turbine may provide power for the electric generator, oil pumps for lubrication, and for landing gears, fuel, oil burner, etc.

The operation of the system may be more clearly understood by giving an illustrative example, as follows: It will be assumed that F-11 is the working fluid; that the heater pressure is 800 lbs. per sq. in., and the temperature a little over 700 F.; that the plane is traveling at high altitude and the ambient temperature is low enough so the condensing temperature is 0 F.

Starting at point A, Fig. 6, one pound of liquid F11, leaving the condenser has the following condition: Temperature=0 F.; pressure=2.55 lbs. abs.; volume- -:.0l92 cu, ft; and heat=7.89 B, t. u.

Sump pump 34 raises its pressure to that of the receiver 31, and it enters the regenerator 24, at point B, where its condition is: T=0 approx.;

=20; H=7.9 B. t. u. In passing through the regenerator 24, it picks up 18.5 B. t. u. (to be explained later). It leaves the regenerator at B and enters the receiver 31. At B its condition is: T=91, P=20, V=.01l0, H=26.4 B. t. u. It now enters the pressure pump 41, where its pressure is raised to 800 lbs. and it enters the heater at C, where its condition is: T= approx.; P=800, H=28.0 B. t. u. (neglecting what it may have obtained from the furnace gases). The increase of temperature and heat from B to C is due to the work done on the liquid by the pump, which equals 1.6 B. t. 11. At C heating from the flame of heater begins, and the temperature of the fluid increases substantially uniformly as it passes through the heater until it crosses the 388 temperature line, when it becomes a vapor. lJt continues along the 800 pressure line until it reaches D, where its condition is: P=800; T=7l0 approx; H=l83 B. t. u. The heat input is HDHc=183--28=155 B. t. 11. At D it enters the turbine and expands to the condenser pressure. The point E represents its condition after expansion. T= approx., P=2.55, V=18.5 approx, H=1l2.5 B. t. u. The energy available for shaft work in the turbineis HD-Hc1.6 (pump) =183--1l2.5'-l.6=68.9 B. t. u. After expansion, the vapor enters the regenerator and imparts most of its remaining superheat to the liquid. Assuming that the liquid entering the regenerator is 0 F., and that in the countercurrent regenerator it can cool the vapor to a temperature differential of 25 F., the vapor would leave the regenerator at 25 F. At point F, its condition is: P=2.55, T'=25 F., V=l5, H=94 B. t. u. The heat transferred to the liquid is heat at E, 94 B. t. u., minus heat at F, 112.5-94 B. t.-u.=l8.5 B. t. u. The vapor now enters the condenser at F and emerges at A as a liquid in the original condition. The heat wasted is heat of the invention has been 86.13. t. u. The cycle is now completed. 1

Heat balance is as follows:

Heat Heat 4 in out Regenerator toliquid BB' 18.5 External heat CD 155.0 Expansion in turbine DE 68. 9 Regenerator from E-'F 18. 5 Condensation 86. l

68 173. 5 173. 5 Thermal efliciency 44.4%

B. t. u. available energy 6 & Q 4. a 6n. it. of vapor to condenser 15 Comparing these figures with steam, the minimum practical working condenser pressure for steam is about V lb; absolute, corresponding to a temperature of 80 F. Expanding steam from 700 F., 800 lbs. to lb. gives a theoretical thermal'efliciency of d1%. The reason why 3-11 is more efllcient is because it can utilize lower condensing temperatures than can be used with steam. I

If the F-ll were heated to 500 F'., point G, and expanded, it would arrive at H on the saturated vapor curve and the regenerator would not be needed. However, the efilciency would be 35.7%, so a gain of 8.7% is achieved by regeneration.

This example, and the diagram, show clearly that the efilciency of this system increases with low temperature and is not affected by altitude, so it is particularly well adapted for low temperature, high altitude flying.

In this system, a central plies several units with power, and provision must be made to prevent all units iromfailing, in the event of the failure of one. Failure due to rupture, as from gun-flre, can occur on the high or low pressure side of the turbine.

source of heat sup- 2, 01,404 at n, 94 B. t. u.,'minus heat at a, 7.89 B. t. u.=

pear to those skilled in the art, may be made without'departing from the scope of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

I claim:

1. A method of converting heat' into work which includes employing a non-inflammable vaporlzable working fluid containing carbon, ch10.- rineand fluorine as essential elements in stable chemical combination; raising the pressure. of the fluid while in the liquid phase, to a pressure near or above its critical pressure; applying external heat to heat said liquid to critical temperature and vaporize it; superheating the vapor to a temperature high enough to ensure dry vapor throughout its desired expansion range; expanding the vapor to desired condensing pressure; utilizing the expansion of said vapor to perform useful work; condensing the vapor to a liquid, and repeating the cycle.

2. A methodof converting heat into work by a thermodynamic cycle of vaporizing, superheating, expanding and liquefying a fluid, which:

method includes employing a. vaporizable noninflammable working fluid containing carbon,

On the high pressure side automatic shut-oi! valves 43 are provided on each pipe leading from the heater.- These valves, 43,- Fig. 5, comprise a valve, 44, normally kept open by a spring, 45. This spring will hold the valve open against the slight throttling of the normal flow of vapor past the valve, but in the eventof a rupture in the high pressure line, the flow will be increased, and

-the valve will seat and remain seated, shutting off the ruptured unit.

If failure occurs in the condensing system and pressure; to perform useful work; applying superheat still remaining in the expanded vapor to preheat the chlorine and fluorine as essential elements in stable .chemical combination; preheating said fluid while in the liquid phase; raising the liquid 7 to a pressure near or above its critical pressure; applying external heat to heat said liquid to critical temperature and to vaporize it; superheating the vapor to a temperature'ensuring dry vapor throughout its desired expansion range; ex

pending the superheated vapor to a condensing utilizing the expansion of said vapor liquid as above specified; condensing the vapor to a liquid, and repeating the cycle.

3. A- method of converting heat into work which includes employing a vaporizablenon-inflamma- 'ble working fluid containing carbon, chlorine and fluorine as essential elements in stable chemical combination; raising the pressure of the fluid while in. the liquid phase, to a pressure. near or above its critical pressure; applying external heat to heat said liquid to critical temperatureand vaporize it; superheatlng the vapor; expanding the vapor to desired condensing pressure; utilizing the expansion of said vapor to perform useful the condenser is below atmospheric pressure, air

will enter the condenser and the eflect will be simply to decrease the efficiency of the unit without putting it out of action.

If the condenser pressure is above atmospheric,

a loss of working fluid will occur.

Gauges 46, showing the condenser pressure for each unit, will show the operator'the condition work; condensing the vapor to a liquid, and repeating the cycle.

4. A method as spec ed in claim 3, and wherein the working fluid is trichloro-monofluoromethane, (CClsF). 5. A method as specified in claim 3, and wherein the working fluid is dichloro-monofluoromethane, (CHClzF) 6. A method as specified in claim 3, and wherein the working fluid is trichloro-trifluoro-etharie,

of each condensing system and indicate whether a unit must be shut down or not.

A liquid level gauge I20 on the receiver will indicate failure or leakage to the liquid lines'orpumps or in the condenser.

The heater can be located in the 'nerable portion of the plane, and can be armored against machine-gun flre. w i

r The lack of vulnerability of this system coupled with the fact that non-inflammable r n can be used renders it safe as possible. Although only one application illustrated and described, other applications,

least vul of the method which will now ap- 7 (CzClaFa). V

"l. A method of converting heat into work by a thermodynamic cycle of vaporizing, su er-heating, expanding and liquefying a fluid, which method includes employing as the working fluid a vaporizable non-inflammable fluid comprising carbon, chlorine and fluorine in stable chemical combination, raising the pressure of said fluid to a pressure between 400and 1000 pounds per square inch, while uid to a temperature between 200 F. and 420 F. to vaporize it without boiling, superheating the vapor to a temperature high enough to ensure dry vapor throughout the desired expansion in'the liquid state, heating said liqrange, expanding said vapor, utilizing the expansion of said vapor to perform useful work,

condensing said vapor to a liquid, and repeating the cycle.

(CClzF) .as the workingfluid, which is 'chemically stable, initially raising the pressure of said fluid from approximately 2.5 pounds per square inch at F. to about 20 pounds per square inch while'in the liquid state, whereby the temperature of said liquid is raised to between 90 F. and

100 F., further raising the pressure of said liquid to approximately 800 pounds per square inch without vaporization, heating said liquid to approximately 388 F. to vaporize it without boiling, superheating the vapor to a temperature between388 F- and 710 F. to ensure dry vapor throughout the desired expansion range, expanding said vapor to a condensing pressure of approximately 2.5 pounds per square inch, utilizing the expansion of said vapor to perform use- .ful work; condensing said vapor to a liquid, and

repeating the cycle.

9'. A method of powering a propeller-driven aircraft by converting heat into work by a thermodynamic cycle of vaporizing, superheating, expanding and liquefying a fluid, which method includes employing as the Working fluid a vaporizable non-inflammable fluid comprising carbon, chlorine and fluorine in stable chemical combination, raising the pressure of said fluid to a pressure between 400 and 1000 pounds persquare men while in the liquid state, heating said liquid to a. temperature between 200 F. and 420 F. to vaporize it without boiling, superheating the vapor to a temperature high enough to ensure dry vapor throughout the. desired expansion range, expanding-said vapor to a desired condensing pressure, utilizing the expansion of said vapor-to drive the aircraft propeller, condensing said vapor to a liquid, and repeating the cycle.

10. A method of'powering a propeller-driven .aircraft by converting Heat into work by a thermodynamic cycle of vaporizing, superheating, ex-

pending and liquefying a fluid, which method said liquid is raised to between 90 F. and 100 F.,

further raising the pressure of said liquid to approximately 800 pounds per square inch without vaporization, heating said liquid to approximately 388 F. to vaporize it without boiling, superheating the vapor to a temperature between 388 F.

and 710 F. to ensure dry vapor throughout the desired expansion range, expanding said vapor to a condensing pressure of approximately 2.5

pounds per square inch, utilizing the expansion of said vapor to drive the aircraft propeller, condensing saidvapor to'a liquid, and repeating the cycle.

11. A method of converting heat into work by a thermodynamic cycle of vaporizing, superheating, expanding and liquefying a fluid, which method includes employing a vaporizable non-inflammable fluid comprising carbon, chlorine and fluorine in stable chemical combination and having the following characteristics: v(a) melting point between -'-30 F. and -252 F. (b) critical pressure between4300 and 1000 pounds per square inch. (0) critical temperature between 200 F. and 500 F. -(d) density between 0.3 and 2.6; raising the pressure of the fluid near-or above its critical pressure while in the liquid phase, heating said liquid to its critical temperature to vaporize it without boiling, superheating the vapor to a temperature high enough to ensure dry vapor throughout the desired expansion range, expanding said vapor to a desired condensing pressure,

' utilizing the expansion of said vapor to perform consists in using trichloro-monofluoro-methane j (CClaF) as the working fluid, which is chemically stable, initially raising the pressure of said fluid from approximately 2,5'ponndsper square-inch at 0 F. to about 20 pounds per square-inch'while in the liquid state, whereby the temperature of useful work, condensing said vapor to a liquid,

and repeating the cycle.

12. A method of converting heat into motive power by a thermodynamic cycle ofvaporizing, superheating, expanding and liquefying a fluid comprising carbon, chlorine and fluorine in stable chemical combination.

13.,A method of converting heat into motive power by a'thermodynamic cycle of vaporizing, superheating, expanding and liquefying a fluid comprising trichloro monofluoro m e t h a n e (CClsF).

14. A method of converting heat into motive power by a thermodynamic cycle of vaporizing, superheating, expanding and liquefying a fluid comprising dichloro-monofluoro-methane (CHClzF) 15. A method of converting heat into motive power by a thermodynamic cycle of vaporizing,

superheating, expanding and liquefying a fluid comprising trichloro-trifluoro-ethane (C2C13F3).

BRADFORD B. HOLMES. 

